Holographic filter with a wide angular field of view and a narrow spectral bandwidth

Abstract

A holographic optical filter that includes an optical recording medium for storing several multiplexed reflection holograms that are formed by successive interference between two or more collimated object beams with a common collimated reference beam. The object beams are incident to the recording material at a series of angles chosen to provide reflection efficiency over the desired filed of view at the specified wavelength.

1. A holographic optical filter, comprising:
 an optical recording medium that stores a multiplexed reflection hologram, the hologram being formed by successive interference between two or more collimated object beams and a common collimated reference beam, 
 the object beams being coherent with the common reference beam and being incident to the optical recording medium at a series of angles chosen to provide reflection efficiency over a selected angular field of view, wherein any light with the same wavelength as the object beams that is incident to the optical recording medium is reflected in a direction parallel to the common reference beam. 
 
     
     
       2. The holographic filter of  claim 1 , wherein any light with wavelength different from the object beams that is incident to the optical recording medium is reflected in a direction at an angle different from that of the common reference beam. 
     
     
       3. The holographic filter of  claim 1 , further comprising a filter that selects a reflected light signal of a desired wavelength and blocks reflected light of undesired wavelengths. 
     
     
       4. The holographic filter of  claim 3 , wherein the filter is a spatial filter. 
     
     
       5. The holographic filter of  claim 4 , wherein the spatial filter includes a lens that focuses the reflected light. 
     
     
       6. The holographic filter of  claim 4 , wherein the spatial filter includes a pin hole. 
     
     
       7. The holographic filter of  claim 1 , wherein the angular field of view includes angles in a single incident plane. 
     
     
       8. The holographic filter of  claim 1 , wherein the angular field of view includes a cone of incident angles. 
     
     
       9. A method of forming a holographic filter, comprising:
 providing an holographic recording medium; and 
 transmitting two or more collimated object beams at the medium from one side of the medium while transmitting a common collimated reference beam from an opposite side of the medium in a manner in which each of the multiple object beams and the reference beam forms a hologram within the holographic recording medium by successive interference of the respective object beam and the reference beam so that the interference patterns are superimposed to form a multiplexed holographic filter, the multiplexed hologram configured to reflect light of a specified wavelength from at least one angle along a common reference beam direction. 
 
     
     
       10. The method of  claim 9 , wherein the multiple object beams are incident to the medium over a series of angles chosen to provide reflection efficiency over the desired angular field of view. 
     
     
       11. The method of  claim 10 , wherein the angular field of view includes angles in a single incident plane. 
     
     
       12. The method of  claim 10 , wherein the angular filed of view includes a cone of incident angles. 
     
     
       13. The method of  claim 9 , wherein the holographic recording medium is made of a photopolymerizable material. 
     
     
       14. The method of  claim 13 , wherein the holographic recording medium has a thickness of about between 50 μm and 5 mm.